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The CLEO CsI Calorimeter 15 Years of Physics with Photons h c ( 1 P 1 charmonium) Discovery M(  c ) (GeV)  c Inclusive  c reconstructed M(  0 -recoil) (2S) 0 h c  0 ( c ) >5.5  significance M(h c )=3524.4 0.60.4 MeV (consistent w/spin-wtd  cJ avg) Requirements

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the cleo csi calorimeter
The CLEO CsI Calorimeter

15 Years of Physics with Photons

CsI to CMS. B. Heltsley. April 2005

h c 1 p 1 charmonium discovery
hc (1P1 charmonium) Discovery

M(c) (GeV)

cInclusive

c reconstructed

M(0-recoil)

(2S)0 hc0(c)

>5.5 significance

M(hc)=3524.40.60.4 MeV

(consistent w/spin-wtd cJ avg)

CsI to CMS. B. Heltsley. April 2005

requirements
Requirements
  • Early 80’s detector landscape
    • Good tracking + poor calorimetry
      • Mark III, CLEO I, Argus
    • Poor tracking + good calorimetry
      • Crystal Ball, CUSB
  • CLEO II: have both!
    • EMCal must fit outside ~1m radius tracking chamber
    • Magnet coil outside EMCal, so EMCal must be compact, work inside B-field

CsI to CMS. B. Heltsley. April 2005

csi tl properties
CsI(Tl) Properties

Light Output

E/E (%)

CsI to CMS. B. Heltsley. April 2005

hermetic coverage
Hermetic Coverage

CsI to CMS. B. Heltsley. April 2005

cleo iii c layout
CLEO III/c Layout

48 rings, 128 per ring

RICH

820/endcap

Drift Chamber

7800 crystals overall

CsI to CMS. B. Heltsley. April 2005

calibrations
Calibrations
  • Electronic channel level
    • Pedestals & Gains on each of 3 ranges
  • Crystal level: conversion factor
  • Shower level: Energy Scale

CsI to CMS. B. Heltsley. April 2005

bhabha calibration
Bhabha Calibration

e+e-

E/E = 1.4%

@5 GeV

Eshower/Ebeam

  • Assume linearity of light  energy
  • Obtain a single constant per crystal: gives relative gain
  • Select e+e- evts: each e has ~Ebeam
  • Minimize shower energy resolution
    • 78007800 sparse matrix equation (non-zero near diagonal)
  • Once determined, why should they change?

CsI to CMS. B. Heltsley. April 2005

light collection degradation
Light Collection Degradation

Crystals migrate from the top band to the bottom band, then stabilize.

Cause: lucite-CsI glue

joint opens up.

CsI to CMS. B. Heltsley. April 2005

absolute energy scale
Absolute Energy Scale
  • 0
  • 
  • +-
  • (2S)cJ

Fit huge

combinatoric

background & subtract

E

CsI to CMS. B. Heltsley. April 2005

current cleo scal
Current CLEO SCal

CsI to CMS. B. Heltsley. April 2005

performance
Performance

Energy resolution

Angular resolution

M (GeV)

CsI to CMS. B. Heltsley. April 2005

non photon rejection
Non-photon rejection
  • Energy deposited near tracks easy to reject on that basis
  • Nuclear int’ns cause “splitoffs” separated from central shower matched to track
  • Splitoffs cause bgd for 0, 
  • Splitoffs make “neutrino reconstruction” (missing energy) more challenging
  • Several algorithms developed for rejection
    • Based on lateral shower profile- collimated or not?
    • Proximity to track entry points
    • Energy

CsI to CMS. B. Heltsley. April 2005

lepton id example 2s j j l l
Lepton ID Example:(2S)+- J/, J/l+l-
  • e deposits ~all energy
  •  deposits ~220 MeV (min. i.) with Landau tail
  • Form “E/p” variable: shower energy/momentum
    • Peak near ~1 for e
    • Only small tail from  at high E/p
    •  peak near small E/p

MC

Data

CsI to CMS. B. Heltsley. April 2005

example 2s 0 0 j j l l
Example: (2S)00 J/, J/l+l-

Very clean,

well-modeled

000

CsI to CMS. B. Heltsley. April 2005

conclusions
Conclusions
  • W/careful design, a CsI(Tl) EMCal offers excellent resolution in energy (1.5-8%) & angle (3-15mr) for E=0.05-5 GeV
  • Long term stability demonstrated (glue joints!)
  • Preserve energy resolution w/careful summing; angular resolution w/MC corrections to c.o.g.
  • Scale calibration a challenge, but can achieve <0.5% accuracy above 50 MeV with some work
  • Shower shape, track-shower matching both useful for isolation & splitoff rejection
  • Payoff in PHYSICS: -lines, 0 & , e & , -reconstruction

CsI to CMS. B. Heltsley. April 2005

crystal testing
Crystal Testing

CsI to CMS. B. Heltsley. April 2005

readout
Readout
  • 4 diodes/crystal
  • Local preamps, 4 crystals/card
  • Externally summed
  • Shaped
  • Digitized (3 scales to preserve dynamic range)
  • Sparsified
  • To tape
  • Disabled diode compensation
        • CLEO has 4 diodes/crystal, can disable & compensate via downloadable settings to crates
    • Output gets amplified up accordingly
    • After 15 yrs, CLEO has 251/7784 crystals w/1 diodes off because they died or became noisy
      • 240 (1 disabled), 11 (2 disabled), 0 (3 or 4 disabled)

CsI to CMS. B. Heltsley. April 2005

dead diodes
Dead Diodes
  • Disabled diode compensation
    • CLEO has 4 diodes/crystal, can disable & compensate via downloadable settings to crates
    • Output gets amplified up accordingly
    • After 15 yrs, CLEO has 251/7784 crystals w/1 diodes off because they died or became noisy
      • 240 (1 disabled), 11 (2 disabled), 0 (3 or 4 disabled)

CsI to CMS. B. Heltsley. April 2005

how many to sum
How many to sum?

Optimize additional energy vs additional noise.

CsI to CMS. B. Heltsley. April 2005

position angle determination
Position/angle determination
  • Correction to centroid:
  • ~0 at ctr
  • ~0 at boundaries
  • not symmetric due to 50-mrad tilt away from vertex-pointing & staggering of front faces
  • smaller effect at larger energy because shower spreads more, which helps centroid accuracy
  • peak correction typically 5-10 mm

CsI to CMS. B. Heltsley. April 2005

shower energy scale
Shower Energy Scale
  • Which do you want?
    •  energy peaks at right place
    • 0 mass peaks at right place
  • You can’t have both, because
    • Line shape has low-side tail (leakage!)
  • W/correct  energy,  mass peaks LOWER than M(0)
  • CLEO chose  energy peak to be accurate, allowing 0 constrained fit to fix the bias

CsI to CMS. B. Heltsley. April 2005